IL91193A - Tumor detection system - Google Patents

Description

91193/3 TUMOR DETECTION SYSTEM Yeda Research and Development Co. Ltd.

Field of the Invention The present invention relates to improvements in apparatus and methods for the detection of tumors in living human tissue generally, and in particular to the early detection of human breast cancer.

Background of the Invention Breast cancer is one of the most pernicious diseases in women. This disease, which is the most common cancer of women in the Western world' and which now attacks one woman in 13, has had a stationary death rate for many years in spite of advances in surgical techniques, radiotherapy and chemotherapy. Statistics show that about 50% of the women succumb to it, in general from the so called metastases.

Therapy of cancer can have much better success the earlier the cancer is detected. Furthermore surgery can be minor if detection is early, avoiding much suffering. It is known that our present methods of surgery, radiotherapy and chemotherapy are effective for long-term survival if applied when the disease is localized to the breast. Since many of the breast cancer cases are not localized when first seen by the clinician, a means must be found to have women present themselves for examination with their disease at an earlier stage than is commonly the case. This means, in a practical way, detection of preclinical cancer in apparently "well" women, when the disease is unsuspected by patient or physician as is the case in mass screening. 1 There are usually two steps in the diagnosis of breast cancer. First the detection of a lesion by a screening method or by self-detection, and then narrowing down the diagnosis, first by non-invasive methods and finally by biopsy, which when positive, is mostly followed by immediate surgical intervention. Such factors as time of examination, radiation dose or cost of the study assume minor roles when evaluating a lesion which has already been detected.

In screening for breast cancer, a large number of women, who presumably have no disease or have only minimal symptoms, is involved in the program. These women would not be having the examination, were it not for the opportunity offered by the screening program. The major thrust in screening is not, therefore, differential diagnosis of a lesion , but the step preceding that, i.e. the detection of an abnormality. All one does in mass screening must be directed to the following objective: the initial detection of an abnormality in the simplest, safest, most accurate and most economical manner possible.

At present the following methods are used for the detection of breast cancer in most clinics : ( 1 ) Clinical examination including: a. Manual palpation; b. Appearance, of the skin; c. Deformation of the breast; (2) X-rays (there are several variants available); Thermography; (4) Transillumination; (5) Ultrasonics.

None of these methods is satisfactory by itself, neither are combinations of these methods fully satisfactory. Cancerous tumors are detected in most cases when several years old. It should also be added that final and reliable diagnosis is only done by biopsy. In many institutions positive diagnosis is obtained in only 25% of biopsies done. It seems therefore obvious that better physical methods for screening of a large number of patients as well as more reliable diagnosis before biopsy would be very important. These methods should also be comfortable and not induce some hesitation in women to visit periodically the clinic. They should also be repeatable any number of times and should not encompass even small health hazards (as X-rays do). The present technology and the large number of patients involved make computer aided devices methods of choice.

Of the presently used methods only thermography lends itself to computerized automation. Success is limited, however, by the rather small number of tumors that cause a rise in temperature of the skin.

U.S. Patent No. 4,291,708 which is hereby incorporated by reference in its entirety, discloses an apparatus for detecting tumors in living human breast tissue comprising: (a) means for determining the dielectric constants of a plurality of localized regions of living human breast tissue including a bridge means . having means for automatically nulling said bridge means while in operation; and (b) means for measuring variations in said dielectric constants over a plurality of said regions and for indicating the possible presence of a tumor as a result of said measurement.

The determining means comprises probe means, in particular a plurality of probe elements.

U.S. Patent No. 4,458,694, which is hereby incorporated by reference in its entirety, discloses an apparatus for detecting tumors in living human breast tissue comprising: (a) means for determining the dielectric constants of localized regions of living human breast tissue including probe means comprising a multiplicity of probe elements; (b) means for applying an AC signal to the tissue; and (c) means for sensing electrical properties at each of said probe elements at a plurality of different times; and (d) signal processing circuitry, coupled to said sensing means for comparing the electrical properties sensed at said plurality of different times for providing an output indication of the dielectric constant of the localized region of breast tissue associated with said probe means.

The probe elements are applied to human breast tissue in vivo, such that individual ones of said probe elements are arranged for sensing characteristics of individual localized regions of human breast tissue.

We have now discovered that when the probe elements have an hexagonal structure, much better results are obtained with the diagnosis made by use of the apparatus described in the above patents .

Summary of the Invention The present invention provides a multielement probe for use in apparatus for detecting tumors in living human tissues based essentially on the determination of the dielectric constant and/or the conductivity values of localized regions of said human tissue, said probe comprising a plurality of planar hexagonal electrodes in a closely spaced geometric pattern, having a distance between adjacent electrodes, each of the electrodes being connected to a detection circuitry.

The invention also provides apparatus for detecting tumors in living human tissues, in particular apparatus as described in U.S. 4,291,708 and U.S. 4,458,694 for detecting breast cancer, comprising the multielement planar hexagonal electrodes of the invention.

Brief Description of the Drawings Fig. 1 is a schematic top view of an electrode pattern of the invention; Fig. 2 is a top view of a hexagonal electrode element; Fig. 3 3a to 3d illustrate various electrode patterns comprising hexagonal elements of the invention.

Detailed Description of the Invention The invention provides a multielement probe for use in an apparatus for detecting tumors in living human tissues based essentially on a determination of electric impedance values of localized regions of the tissues, which probe comprises a plurality of planar hexagonal electrodes in a closely spaced geometric pattern, having a distance between adjacent electrodes, each of the electrodes being connected to a detection circuitry. The hexagonal electrodes are part of a printed circuit pattern.

A tumor detection system comprising said multielement probe is provided which contains means for applying an AC signal to the tissue beneath each such electrode, means for sensing the electrical properties of such tissue, and signal processing means providing an output indicative of the dielectric properties of each such region of the tissue. It may also comprise means for the repetitive application of such AC signals, and for evaluating the resulting signals, determining dielectric properties of regions of the tissue beneath each electrode sensor.

The probe comprises hexagonal electrodes arranged in consecutive rows, where the hexagonal elements i any consecutive row are displaced respective to the preceding row by half the width of the hexagon. There are also provided means for switching from one sensor to a predetermined number of sensors, and means for evaluating the results of such varying sensors . The measurements are made by means of 1 , 3 5 or 7 electrodes , or with any combination of such electrode sensors at any given time.

The main information needed is obtained, by findings of inhomogeneities in the breast. The impedance of a specific area depends on the . dielectric constant and the conductivity of the tissue, as well as on the spatial relations of any entity of tissue to its surrounding tissue and the measuring electrode. No definite values can be associated with specific pathologies, even inside a tumor the values vary according to stages of development. Healthy tissue is in general fairly homogeneous.

Whereas in the use of single electrodes, circular electrodes are preferred, for dielectric measurements of the type dealt with in this application, there have been used electrodes comprising a plurality of square elements arranged in a closely arranged geometrical arrangement with little space between adjoining electrode elements. One example is square shaped probe made of polyvinylchloride plastic that is placed by the operator on the breast of the patient; the active area of the probe contains an 8 x 8 matrix of square electrodes (of 7.mm each side); the electrodes are gold plated printed copper.

According to the present invention there are · provided electrodes for the same use, which have advantageous electrode elements, each of which is connected to monitoring means .

There exist various alternatives for such arrangements . One of these is set out' in Fig. 1, where rows of hexagonal elements are arranged in a pattern- with a rectangular outline. The parallel sides of the hexagons of the first row should be near each other, the second row is displaced to provide a fitting pattern, the third row is like the first one, the fourth like the second and so on. In this way, one gets more use of the useful electrode area against the useless interelectrode area. Better definition in area and more indepth resolution will result. The outline is within the confines of a rectangle, but without straight-line boundaries, which define a meandering path.

The pattern of Fig. 1 results in an increased efficiency of the measurement and better utilization of electrode area, with a better indepth resolution. Such advantage results from several factors . The borders of the electrodes or in most cases the unavoidable space between results in a loss of measurement capability. This results from the LaPlace equation which governs the electric fields created with these electrodes. Therefore a shape of maximum area to minimum border is best. On the other hand, the electrodes must have a shape that covers the field, in other words they much fit together. If one wants to use only one geometric type of electrode, hexagonal are superior to square ones. Although a combination of different shapes could be better in this respect, it would create difficulties in the handling of currents to be supplied to such a combination of electrodes, the handling of information derived from these, and therefore would result in very complicated and more costly computing means .

Another consideration to give preference to hexagonal electrodes is the field distortion, which results, from the border of the electrodes, the so-called "edge effect" (in German Rand Effekt) . This effect propagates into the field increasingly according to the LaPlace equation, and blurring occurs wiht increasing depth. This means that for investigation near to the surface (skin), one should use a probe with small electrodes, whereas for deeper depths, larger electrodes should be used, as they give better penetration. It would be most inconvenient and a waste of time to change from one probe to the other. It is possible to have the computer circuitry connect several electrodes together in ever increasing numbers. This can give images of ever increasing depths. On the monitoring screen this can also be represented by using differing colors for different depths or alternatively by having each "pixel" consist of different rings analogous to the different depths, as shown in Fig. 2.

Hexagonal electrodes have the advantage that they allow inter-connection for depth penetration in smaller steps (1,3,6,7) , whereas square electrodes allow grouping only in larger steps (1,4,9), as long as one keeps to the condition of maximum area to minimum border (see Fig. 3).

The part close to the skin is represented by the center of the pixel, the outer part by depth information, adjacent pixels will then, in many cases, have a similar coloring in the outer rings , conforming to the ever lower definition with depth. Several advantages result from using hexagonal electrodes (pixel) as outlined above.

It has . been found, both theoretically and practically, that corners on contact electrodes of the type used in measurements of the invention, constitute waste as the field which emanates from them disperses more rapidly, the sharper such corners are.

From a theoretical point of view circular electrodes would be the best as they have a minimum border length per unit area. In this present case they cannot be used as a dense cover of the entire surface is required. The electrode system of the invention is the optimum one, if only one shape of electrode elements is required. This comprises a plurality of hexagonal electrode elements, in a geometrical arrangement where the hexagonal elements are provided in a close fit pattern, with a minimum distance between adjacent elements .

It is clear that the ratio of area to circumference is a better one with hexagons than with squares. A hexagonal electrode with sides of 1 cm lenght have a circumference of 6 cm and an area of 2.58 cm2 versus a square of similar area (2.56 cm2) which has sides of 1.6 and a circumference of 6. cm.

According to a preferred embodiment of the invention, the array of electrodes of hexagonal shape are part of a generally planar printed circuit, which circuit also provides the required electrical connection for connecting at will at the same time any number and pattern of electrode sensors, and for the rapid switching betwwen various numbers and configurations of the sensors used for specific measurements, the evaluation being effected generally by suitable computer means .

A variety of hexagonal electrodes was evaluated, and it was found that hexagons with sides of about 10 mm give satisfactory results. This specific parameter is only indicative and not to be construed in a restrictive sense.

The electrode pattern of the invention is a highly effective one and generally good results are obtained up to a depth which equals about 3 times the linear dimensions of the electrode. i I. Λ. - Ό 91193/3

Claims (8)

1. A multielement probe for use in an apparatus for detecting tumors in living human tissues based essentially on a determination of electric impedance values of localized regions of the tissues, which probe comprises a plurality of planar hexagonal electrodes in a closely spaced geometric pattern, having a distance between adjacent electrodes, each of the electrodes being connected to a detection circuitry.

2. A tumor detection system for detecting tumors in living human tissues based essentially on a determination of electric impedance values of localized regions of the tissue, comprising a probe according to claim 1.

3. A tumor detection system according to claim 2 , comprising a detection circuitry which contains means for applying an AC signal to the tissue beneath each said electrode, means for sensing the electrical properties of the tissue based upon the AC signal applied to the tissue, and signal processing means providing an output indicative of the dielectric properties of each such region of the tissue.

4. A tumor detection system according to claim 3 , comprising means for the repetitive application of said AC signals, and means for evaluating the resulting signals, determining dielectric properties of regions of the tissue beneath each electrode sensor. 91193/3

5. A tumor detection system according to claim 2 , in which said hexagonal electrodes are arranged in consecutive rows, and the rows of electrodes are displaced respective to a preceding row by half the width of the hexagonal electrode.

6. A tumor detection system according to claim 1 in which the hexagonal electrodes are part of a pattern of a printed circuit.

7. A tumor detection system according to claim 3 , where means are provided for switching from one electrode to a combination of a predetermined number of electrodes , and means for evaluating the results of such combination of electrodes.

8. A system according to claim 6 , where measurements are made by means of 1 , 3 , 5 or 7 electrodes , or with any combination of electrodes at any given time. For the Applicants Paulina Ben-Ami Patent Attorney